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Abstract:

The present invention is generally directed to electroluminescent Ir(III)
compounds, the substituted 2-phenylpyridines, phenylpyrimidines, and
phenylquinolines that are used to make the Ir(III) compounds, and devices
that are made with the Ir(III) compounds.

Claims:

1-11. (canceled)

12. (canceled)

13. An electronic device comprising an organic layer comprising at least
one Ir(III) compound made from precursor compounds having a structure set
forth below: ##STR00011##

14. An electronic device comprising a light emitting layer comprising at
least one Ir(III) compound made from precursor compounds having the
structure set forth in claim 13.

15. An electronic device comprising a charge transport layer comprising at
least one Ir(III) compound made from precursor compounds having the
structure set forth in claim 13.

16. An electronic device comprising an organic layer comprising at least
one Ir(III) compound made from precursor compounds having the following
structure: ##STR00012##

17. The device of claim 16, wherein the organic layer is a light-emitting
layer.

18. The device of claim 16, wherein the organic layer is a charge
transport layer.

Description:

RELATED APPLICATION

[0001]This application is a continuation-in-part application of U.S.
patent application Ser. No. 09/879,014, filed on Jun. 12, 2001, now
pending, which claims the benefit of U.S. provisional application Ser.
No. 60/215,362 filed on Jun. 30, 2000 and claims the benefit of U.S.
provisional application Ser. No. 60/224,273 filed on Aug. 10, 2000.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]This invention relates to electroluminescent complexes of
iridium(III) with fluorinated phenylpyridines, phenylpyrimidines, and
phenylquinolines. It also relates to electronic devices in which the
active layer includes an electroluminescent Ir(III) complex.

[0004]2. Description of the Related Art

[0005]Organic electronic devices that emit light, such as light-emitting
diodes that make up displays, are present in many different kinds of
electronic equipment. In all such devices, an organic active layer is
sandwiched between two electrical contact layers. At least one of the
electrical contact layers is light-transmitting so that light can pass
through the electrical contact layer. The organic active layer emits
light through the light-transmitting electrical contact layer upon
application of electricity across the electrical contact layers.

[0006]It is well known to use organic electroluminescent compounds as the
active component in light-emitting diodes. Simple organic molecules such
as anthracene, thiadiazole derivatives, and coumarin derivatives are
known to show electroluminescence. Semiconductive conjugated polymers
have also been used as electroluminescent components, as has been
disclosed in, for example, Friend et al., U.S. Pat. No. 5,247,190, Heeger
et al., U.S. Pat. No. 5,408,109, and Nakano et al., Published European
Patent Application 443 861. Complexes of 8-hydroxyquinolate with
trivalent metal ions, particularly aluminum, have been extensively used
as electroluminescent components, as has been disclosed in, for example,
Tang et al., U.S. Pat. No. 5,552,678.

[0007]Burrows and Thompson have reported that fac-tris(2-phenylpyridine)
iridium can be used as the active component in organic light-emitting
devices. (Appl. Phys. Lett. 1999, 75, 4.) The performance is maximized
when the iridium compound is present in a host conductive material.
Thompson has further reported devices in which the active layer is
poly(N-vinyl carbazole) doped with
fac-tris[2-(4',5'-difluorophenyl)pyridine-C'2,N]iridium(III).
(Polymer Preprints 2000, 41(1), 770.)

[0008]However, there is a continuing need for electroluminescent compounds
having improved efficiency.

SUMMARY OF THE INVENTION

[0009]The present invention is directed to an iridium compound (generally
referred as "Ir(III) compounds") having at least two 2-phenylpyridine
ligands in which there is at least one fluorine or fluorinated group on
the ligand. The iridium compound has the following First Formula:

IrLaLbLcxL'yL''z (First Formula)

[0010]where: [0011]x=0 or 1, y=0, 1 or 2, and z=0 or 1, with the proviso
that: [0012]x=0 or y+z=0 and [0013]when y=2 then z=0; [0014]L'=a
bidentate ligand or a monodentate ligand, and is not a phenylpyridine,
phenylpyrimidine, or phenylquinoline; with the proviso that: [0015]when
L' is a monodentate ligand, y+z=2, and [0016]when L' is a bidentate
ligand, z=0; [0017]L''=a monodentate ligand, and is not a
phenylpyridine, and phenylpyrimidine, or phenylquinoline; and
[0018]La, Lb and Lc are alike or different from each other
and each of La, Lb and Lc has structure (I) below:

##STR00001##

[0019]wherein: [0020]adjacent pairs of R1 through R4 and
R5 through R8 can be joined to form a five- or six-membered
ring, [0021]at least one of R1 through R8 is selected from F,
CnF2n+1, OCnF2n+1, and OCF2X, where n is an
integer from 1 through 6 and X═H, Cl, or Br, and [0022]A=C or N,
provided that when A=N, there is no R1.

[0023]In another embodiment, the present invention is directed to
substituted 2-phenylpyridine, phenylpyrimidine, and phenylquinoline
precursor compounds from which the above Ir(III) compounds are made. The
precursor compounds have a structure (II) or (III) below:

##STR00002##

[0024]where A and R1 through R8 are as defined in structure (1)
above, [0025]and R9 is H.

##STR00003##

[0026]where: [0027]at least one of R10 through R19 is selected
from F, CnF2n+1, OCnF2n+1, and OCF2X, where n=an
integer between 1 and 6 and X is H, Cl, or Br, and R20 is H.

[0028]It is understood that there is free rotation about the
phenyl-pyridine, phenyl-pyrimidine and the phenyl-quinoline bonds.
However, for the discussion herein, the compounds will be described in
terms of one orientation.

[0029]In another embodiment, the present invention is directed to an
organic electronic device having at least one emitting layer comprising
the above Ir(III) compound, or combinations of the above Ir(III)
compounds.

[0030]As used herein, the term "compound" is intended to mean an
electrically uncharged substance made up of molecules that further
consist of atoms, wherein the atoms cannot be separated by physical
means. The term "ligand" is intended to mean a molecule, ion, or atom
that is attached to the coordination sphere of a metallic ion. The term
"complex", when used as a noun, is intended to mean a compound having at
least one metallic ion and at least one ligand. The term "group" is
intended to mean a part of a compound, such a substituent in an organic
compound or a ligand in a complex. The term "facial" is intended to mean
one isomer of a complex, Ma3b3, having octahedral geometry, in
which the three "a" groups are all adjacent, i.e. at the corners of one
face of the octahedron. The term "meridional" is intended to mean one
isomer of a complex, Ma3b3, having octahedral geometry, in
which the three "a" groups occupy three positions such that two are trans
to each other. The phrase "adjacent to," when used to refer to layers in
a device, does not necessarily mean that one layer is immediately next to
another layer. On the other hand, the phrase "adjacent R groups," is used
to refer to R groups that are next to each other in a chemical formula
(I.e., R groups that are on atoms joined by a bond). The term
"photoactive" refers to any material that exhibits electroluminescence
and/or photosensitivity. The term "(H+F)" is intended to mean all
combinations of hydrogen and fluorine, including completely hydrogenated,
partially fluorinated or perfluorinated substituents. By "emission
maximum" is meant the wavelength, in nanometers, at which the maximum
intensity of electroluminescence is obtained. Electroluminescence is
generally measured in a diode structure, in which the material to be
tested is sandwiched between two electrical contact layers and a voltage
is applied. The light intensity and wavelength can be measured, for
example, by a photodiode and a spectrograph, respectively.

DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a schematic diagram of a light-emitting device (LED).

[0032]FIG. 2 is a schematic diagram of an LED testing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033]The Ir(III) compounds of the invention have the First Formula
Ir(III)LaLbLcxL'y above.

[0034]The above Ir(III) compounds are frequently referred to as
cyclometalated complexes: Ir(III) compounds having the following Second
Formula is also frequently referred to as a bis-cyclometalated complex.:

IrLaLbL'yL''z (Second Formula)

[0035]where: [0036]y, z, La, Lb, L', and L'' are as defined in
the First Formula above.Ir(III) compounds having the following Third
Formula is also frequently referred to as a tris-cyclometalated complex.:

[0036]IrLaLbLc (Third Formula)

[0037]where: [0038]La, Lb and Lc are as defined in the
First Formula described above.

[0039]The preferred cyclometalated complexes are neutral and non-ionic,
and can be sublimed intact. Thin films of these materials obtained via
vacuum deposition exhibit good to excellent electroluminescent
properties. Introduction of fluorine substituents into the ligands on the
iridium atom increases both the stability and volatility of the
complexes. As a result, vacuum deposition can be carried out at lower
temperatures and decomposition of the complexes can be avoided.
Introduction of fluorine substituents into the ligands can often reduce
the non-radiative decay rate and the self-quenching phenomenon in the
solid state. These reductions can lead to enhanced luminescence
efficiency. Variation of substituents with electron-donating and
electron-withdrawing properties allows for fine-tuning of
electroluminescent properties of the compound and hence optimization of
the brightness and efficiency in an electroluminescent device.

[0040]While not wishing to be bound by theory, it is believed that the
emission from the iridium compounds is ligand-based, resulting from
metal-to-ligand charge transfer. Therefore, compounds that can exhibit
electroluminescence include those of compounds of the Second Formula
IrLaLbL'yL''z above, and the Third Formula
IrLaLbLc above, where all La, Lb, and Lc in
the Third Formula are phenylpyridines, phenylpyrimidines, or
phenylquinolines. The R1 through R8 groups of structures (I)
and (II), and the R10 through R19 groups of structure (III)
above may be chosen from conventional substitutents for organic
compounds, such as alkyl, alkoxy, halogen, nitro, and cyano groups, as
well as fluoro, fluorinated alkyl and fluorinated alkoxy groups. The
groups can be partially or fully fluorinated (perfluorinated). Preferred
iridium compounds have all R1 through R8 and R10 through
R19 substituents selected from fluoro, perfluorinated alkyl
(CnF2n+1) and perfluorinated alkoxy groups
(OCnF2n+1), where the perfluorinated alkyl and alkoxy groups
have from 1 through 6 carbon atoms, or a group of the formula OCF2X,
where X is H, Cl, or Br.

[0041]It has been found that the electroluminescent properties of the
cyclometalated iridium complexes are poorer when any one or more of the
R1 through R8 and R10 through R19 groups is a nitro
group. Therefore, it is preferred that none of the R1 through
R8 and R10 through R19 groups is a nitro group.

[0042]It has been found that the luminescence efficiency of the
cyclometalated iridium complexes may be improved by using phenylpyridine,
phenylpyrimidine, and phenylquinoline ligands in which some or all of the
hydrogens have been replaced with deuterium.

[0043]The nitrogen-containing ring can be a pyridine ring, a pyrimidine or
a quinoline. It is preferred that at least one fluorinated substituent is
on the nitrogen-containing ring; most preferably CF3.

[0044]Any conventional ligands known to transition metal coordination
chemistry is suitable as the L' and L'' ligands. Examples of bidentate
ligands include compounds having two coordinating groups, such as
ethylenediamine and acetylacetonate, which may be substituted. Examples
of anionic bidentate ligands include beta-enolates, such as
acetylacetonate; the anionic form of hydroxyquinolines, such as
8-hydroxyquinoline, which may be substituted, in which the H from the
hydroxy group has been extracted; aminocarboxylates; iminocarboxylates,
such as pyridine carboxylate; salicylates; salicylaldimines, such as
2-[(phenylimino)methyl]phenol; and phosphinoalkoxides, such as
3-(diphenylphosphino)-1-propoxide. Examples of monodentate ligands
include chloride and nitrate ions; phosphines; isonitriles; carbon
monoxide; and mono-amines. It is preferred that the iridium complex be
neutral and sublimable. If a single bidentate ligand is used, it should
have a net charge of minus one (-1). If two monodentate ligands are used,
they should have a combined net charge of minus one (-1). The
bis-cyclometalated complexes can be useful in preparing
tris-cyclometalated complexes where the ligands are not all the same.

[0045]In a preferred embodiment, the iridium compound has the Third
Formula IrLaLbLc as described above.

[0046]In a more preferred embodiment, La=Lb=Lc. These more
preferred compounds frequently exhibit a facial geometry, as determined
by single crystal X-ray diffraction, in which the nitrogen atoms
coordinated to the iridium are trans with respect to carbon atoms
coordinated to the iridium. These more preferred compounds have the
following Fourth Formula:

fac-Ir(La)3 (Fourth Formula) [0047]where La has
structure (I) above.The compounds can also exhibit a meridional geometry
in which two of the nitrogen atoms coordinated to the iridium are trans
to each other. These compounds have the following Fifth Formula:

[0051]The iridium complexes of the Third Formula IrLaLbLc
above are generally prepared from the appropriate substituted
2-phenylpyridine, phenylpyrimidine, or phenylquinoline. The substituted
2-phenylpyridines, phenylpyrimidines, and phenylquinolines, as shown in
Structure (II) above, are prepared, in good to excellent yield, using the
Suzuki coupling of the substituted 2-chloropyridine, 2-chloropyrimidine
or 2-chloroquinoline with arylboronic acid as described in O. Lohse, P.
Thevenin, E. Waldvogel Synlett, 1999, 45-48. This reaction is illustrated
for the pyridine derivative, where X and Y represent substituents, in
Equation (1) below:

##STR00005##

[0052]Examples of 2-phenylpyridine and 2-phenylpyrimidine compounds,
having structure (II) above, are given in Table 2 below:

[0053]One example of a substituted 2-phenylquinoline compound, having
structure (III) above, is compound 2-u, which has R17 is CF3
and R10 through R16 and R18 through R20 are H.

[0054]The 2-phenylpyridines, pyrimidines, and quinolines thus prepared are
used for the synthesis of the cyclometalated iridium complexes. A
convenient one-step method has been developed employing commercially
available iridium trichloride hydrate and silver trifluoroacetate. The
reactions are generally carried out with an excess of 2-phenylpyridine,
pyrimidine, or quinoline, without a solvent, in the presence of 3
equivalents of AgOCOCF3. This reaction is illustrated for a
2-phenylpyridine in Equation (2) below:

##STR00006##

The tris-cyclometalated iridium complexes were isolated, purified, and
fully characterized by elemental analysis, 1H and 19F NMR
spectral data, and, for compounds 1-b, 1-c, and 1-e, single crystal X-ray
diffraction. In some cases, mixtures of isomers are obtained. Often the
mixture can be used without isolating the individual isomers.

[0055]The iridium complexes having the Second Formula
IrLaLbL'yL''z above, may, in some cases, be isolated
from the reaction mixture using the same synthetic procedures as
preparing those having Third Formula IrLaLbLc above. The
complexes can also be prepared by first preparing an intermediate iridium
dimer having structure (VII) below:

##STR00007##

[0056]wherein: [0057]B=H, CH3, or C2H5, and
[0058]La, Lb, Lc, and Ld can be the same or different
from each other and each of La, Lb, Lc, and Ld has
structure (I) above.

[0059]The iridium dimers can generally be prepared by first reacting
iridium trichloride hydrate with the 2-phenylpyridine, phenylpyrimidine
or phenylquinoline, and adding NaOB.

[0061]This intermediate can be used to prepare compound 1-p by the
addition of ethyl acetoacetate.

[0062]Of particular interest, are complexes in which the emission has a
maximum in the red region of the visible spectrum, from 570 to 625 nm for
red-orange, and from 625 to 700 nm for red. It has been found that the
emission maxima of complexes of the Second and Third Formulae are shifted
to the red when L has structure (XI) below, derived from a
phenyl-quinoline compound having structure (III) above, or when L has
structure (XII) below, derived from a phenyl-isoquinoline compound:

##STR00009##

[0063]where: [0064]at least one of R10 through R19 is selected
from F, CnF2n+1, OCnF2n+1, and OCF2X, where n is an
integer from 1 through 6 and X is H, Cl, or Br;

##STR00010##

[0065]where: [0066]at least one of R21 through R30 is selected
from F, [0067]CnF2n+1, OCnF2n+1, and OCF2X, where n
is an integer from 1 through 6 and X is H, Cl, or Br.

[0068]It has also been found that the ligands of the invention can have
perfluoroalkyl and perfluoroalkoxy substituents with up to 12 carbon
atoms.

[0069]In the Second Formula, the L' and L'' ligands in the complex can be
selected from any of those listed above, and are preferably chosen so
that the overall molecule is uncharged. Preferably, z is 0, and L' is a
monoanionic bidentate ligand, that is not a phenylpyridine,
phenyhlpyrimidine, or phenylquinoline.

[0070]Although not preferred, complexes of the Second Formula also have
emission maxima that are shifted to the red when L is a phenylpyridine
ligand with structure (I) above, and L' is a bidentate hydroxyquinolate
ligand.

[0071]Examples of compounds of the Second Formula, where La is the
same as Lb, L' is a bidentate ligand, y is 1, and z is 0, and
compounds of the Third Formula where La, Lb, and Lc are
the same, are given in Table 8 below. When L has structure (I) above, A
is C. In this table, "acac" stands for 2,4-pentanedionate; "8hq" stands
for 8-hydroxyquinolinate; "Me-8hq" stands for
2-methyl-8-hydroxyquinolinate.

[0072]The complexes in Table 8 have emission maxima in the range of about
590 to 650 nm.

[0073]Also of particular interest, are complexes in which the emission has
a maximum in the blue region of the visible spectrum, from about 450 to
500 nm. It has been found that the photoluminescence and
electroluminescence of the complexes are shifted to the blue when the
complex has the Second Formula where La and Lb are
phenyl-pyridine ligands with an additional ligand selected from a
phosphine, an isonitrile, and carbon monoxide. Suitable complexes have
the Sixth Formula below:

IrLaLbL'L'' (Sixth Formula)

[0074]where [0075]L' is selected from a phosphine, an isonitrile, and
carbon monoxide; [0076]L'' is selected from F, Cl, Br, and I
[0077]La and Lb are alike or different and each of La and
Lb has structure (I) above, wherein: [0078]R1 through R8
are independently selected from alkyl, alkoxy, halogen, nitro, cyano,
fluoro, fluorinated alkyl and fluorinated alkoxy groups, and at least one
of R1 through R8 is selected from F, CnF2n+1,
OCnF2n+1, and OCF2X, where n is an integer from 1 through
6 and X is H, Cl, or Br, and A is C.

[0079]The phosphine ligands in the Sixth Formula preferably have the
Seventh Formula below

P(Ar)3 (Seventh Formula)

where Ar is an aromatic group, preferably a phenyl group, which may have
alkyl or aryl substituents. Most preferably, the Ar group is a phenyl
group having at least one fluorine or fluorinated alkyl substituent.
Examples of suitable phosphine ligands include (with the abbreviation
provided in brackets): [0080]triphenylphosphine [PPh3]
[0081]tris[3,5-bis(trifluoromethyl)phenyl]phosphine [PtmPh3]Some of the
phosphine compounds are available commercially, or they can be prepared
using any of numerous well-known synthetic procedures, such as alkylation
or arylation reactions of PCl3 or other P-electrophiles with
organolithium or organomagnesium compounds.

[0082]The isonitrile ligands in the Sixth Formula, preferably have
isonitrile substituents on aromatic groups. Examples of suitable
isonitrile ligands include (with the abbreviation provided in brackets):

[0083]2,6-dimethylphenyl isocyanide [NC-1]

[0084]3-trifluoromethylphenyl isocyanide [NC-2]

[0085]4-toluenesulfonylmethyl isocyanide [NC-3]

Some of the isonitrile compounds are available commercially. They also can
be prepared using known procedures, such as the Hofmann reaction, in
which the dichlorocarbene is generated from chloroform and a base in the
presence of a primary amine.

[0086]It is preferred that L'' in the Sixth Formula is chloride. It is
preferred that La is the same as Lb.

[0087]Examples of compounds of the Sixth Formula where La is the same
as Lb and L'' is chloride, are given in Table 9 below, where R1
through R8 are as shown in structure (I) above.

[0088]The complexes in Table 9 have emission maxima in the range of about
450 to 550 nm.

Electronic Device

[0089]The present invention also relates to an electronic device
comprising at least one photoactive layer positioned between two
electrical contact layers, wherein the at least one layer of the device
includes the iridium complex of the invention. Devices frequently have
additional hole transport and electron transport layers. A typical
structure is shown in FIG. 1. The device 100 has an anode layer 110 and a
cathode layer 150. Adjacent to the anode is a layer 120 comprising hole
transport material. Adjacent to the cathode is a layer 140 comprising an
electron transport material. Between the hole transport layer and the
electron transport layer is the photoactive layer 130. Layers 120, 130,
and 140 are individually and collectively referred to as the active
layers.

[0090]Depending upon the application of the device 100, the photoactive
layer 130 can be a light-emitting layer that is activated by an applied
voltage (such as in a light-emitting diode or light-emitting
electrochemical cell), a layer of material that responds to radiant
energy and generates a signal with or without an applied bias voltage
(such as in a photodetector). Examples of photodetectors include
photoconductive cells, photoresistors, photoswitches, phototransistors,
and phototubes, and photovoltaic cells, as these terms are describe in
Markus, John, Electronics and Nucleonics Dictionary, 470 and 476
(McGraw-Hill, Inc. 1966).

[0091]The iridium compounds of the invention are particularly useful as
the photoactive material in layer 130, or as electron transport material
in layer 140. Preferably the iridium complexes of the invention are used
as the light-emitting material in diodes. It has been found that in these
applications, the fluorinated compounds of the invention do not need to
be in a solid matrix diluent in order to be effective. A layer that is
greater than 20% by weight iridium compound, based on the total weight of
the layer, up to 100% iridium compound, can be used as the emitting
layer. This is in contrast to the non-fluorinated iridium compound,
tris(2-phenylpyridine) iridium (III), which was found to achieve maximum
efficiency when present in an amount of only 6 to 8% by weight in the
emitting layer. This was necessary to reduce the self-quenching effect.
Additional materials can be present in the emitting layer with the
iridium compound. For example, a fluorescent dye may be present to alter
the color of emission. A diluent may also be added. The diluent can be a
polymeric material, such as poly(N-vinyl carbazole) and polysilane. It
can also be a small molecule, such as 4,4'-N,N'-dicarbazole biphenyl or
tertiary aromatic amines. When a diluent is used, the iridium compound is
generally present in a small amount, usually less than 20% by weight,
preferably less than 10% by weight, based on the total weight of the
layer.

[0092]In some cases the iridium complexes may be present in more than one
isomeric form, or mixtures of different complexes may be present. It will
be understood that in the above discussion of OLEDs, the term "the
iridium compound" is intended to encompass mixtures of compounds and/or
isomers.

[0093]To achieve a high efficiency LED, the HOMO (highest occupied
molecular orbital) of the hole transport material should align with the
work function of the anode, the LUMO (lowest unoccupied molecular
orbital) of the electron transport material should align with the work
function of the cathode. Chemical compatibility and sublimation temp of
the materials are also important considerations in selecting the electron
and hole transport materials.

[0094]The other layers in the OLED can be made of any materials which are
known to be useful in such layers. The anode 110, is an electrode that is
particularly efficient for injecting positive charge carriers. It can be
made of, for example materials containing a metal, mixed metal, alloy,
metal oxide or mixed-metal oxide, or it can be a conducting polymer.
Suitable metals include the Group 11 metals, the metals in Groups 4, 5,
and 6, and the Group 8 through 10 transition metals. If the anode is to
be light-transmitting, mixed-metal oxides of Groups 12, 13 and 14 metals,
such as indium-tin-oxide, are generally used. The IUPAC numbering system
is used throughout, where the groups from the Periodic Table are numbered
from left to right as 1 through 18 (CRC Handbook of Chemistry and
Physics, 81St Edition, 2000). The anode 110 may also comprise an organic
material such as polyaniline as described in "Flexible light-emitting
diodes made from soluble conducting polymer," Nature vol. 357, pp 477-479
(11 Jun. 1992). At least one of the anode and cathode should be at least
partially transparent to allow the generated light to be observed.

[0096]Examples of electron transport materials for layer 140 include metal
chelated oxinoid compounds, such as tris(8-hydroxyquinolato)aluminum
(Alq3); phenanthroline-based compounds, such as
2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA) or
4,7-diphenyl-1,10-phenanthroline (DPA), and azole compounds such as
2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) and
3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ). Layer
140 can function both to facilitate electron transport, and also serve as
a buffer layer or confinement layer to prevent quenching of the exciton
at layer interfaces. Preferably, this layer promotes electron mobility
and reduces exciton quenching.

[0097]The cathode 150, is an electrode that is particularly efficient for
injecting electrons or negative charge carriers. The cathode can be any
metal or nonmetal having a lower work function than the anode. Materials
for the cathode can be selected from alkali metals of Group 1 (e.g., Li,
Cs), the Group 2 (alkaline earth) metals, the Group 12 metals, including
the rare earth elements and lanthanides, and the actinides. Materials
such as aluminum, indium, calcium, barium, samarium and magnesium, as
well as combinations, can be used. Li-containing organometallic compounds
can also be deposited between the organic layer and the cathode layer to
lower the operating voltage.

[0098]It is known to have other layers in organic electronic devices. For
example, there can be a layer (not shown) between the conductive polymer
layer 120 and the active layer 130 to facilitate positive charge
transport and/or band-gap matching of the layers, or to function as a
protective layer. Similarly, there can be additional layers (not shown)
between the active layer 130 and the cathode layer 150 to facilitate
negative charge transport and/or band-gap matching between the layers, or
to function as a protective layer. Layers that are known in the art can
be used. In addition, any of the above-described layers can be made of
two or more layers. Alternatively, some or all of inorganic anode layer
110, the conductive polymer layer 120, the active layer 130, and cathode
layer 150, may be surface treated to increase charge carrier transport
efficiency. The choice of materials for each of the component layers is
preferably determined by balancing the goals of providing a device with
high device efficiency.

[0099]It is understood that each functional layer may be made up of more
than one layer.

[0100]The device can be prepared by sequentially vapor depositing the
individual layers on a suitable substrate. Substrates such as glass and
polymeric films can be used. Conventional vapor deposition techniques can
be used, such as thermal evaporation, chemical vapor deposition, and the
like. Alternatively, the organic layers can be coated from solutions or
dispersions in suitable solvents, using any conventional coating
technique. In general, the different layers will have the following range
of thicknesses: anode 110, 500 to 5000 Å, preferably 1000 to 2000
Å; hole transport layer 120, 50 to 1000 Å, preferably 200 to 800
Å; light-emitting layer 130, 10 to 1000 Å, preferably 100 to 800
Å; electron transport layer 140, 50 to 1000 Å, preferably 200 to
800 Å; cathode 150, 200 to 10000 Å, preferably 300 to 5000 Å.
The location of the electron-hole recombination zone in the device, and
thus the emission spectrum of the device, can be affected by the relative
thickness of each layer. Thus the thickness of the electron-transport
layer should be chosen so that the electron-hole recombination zone is in
the light-emitting layer. The desired ratio of layer thicknesses will
depend on the exact nature of the materials used.

[0101]It is understood that the efficiency of devices made with the
iridium compounds of the invention, can be further improved by optimizing
the other layers in the device. For example, more efficient cathodes such
as Ca, Ba or LiF can be used. Shaped substrates and novel hole transport
materials that result in a reduction in operating voltage or increase
quantum efficiency are also applicable. Additional layers can also be
added to tailor the energy levels of the various layers and facilitate
electroluminescence.

[0102]The iridium complexes of the invention often are phosphorescent and
photoluminescent and may be useful in applications other than OLEDs. For
example, organometallic complexes of iridium have been used as oxygen
sensitive indicators, as phosphorescent indicators in bioassays, and as
catalysts. The bis cyclometalated complexes can be used to sythesize tris
cyclometalated complexes where the third ligand is the same or different.

EXAMPLES

[0103]The following examples illustrate certain features and advantages of
the present invention. They are intended to be illustrative of the
invention, but not limiting. All percentages are by weight, unless
otherwise indicated.

Example 1

[0104]This example illustrates the preparation of the 2-phenylpyridines
and 2-phenylpyrimidines which are used to form the iridium compounds.

[0105]The general procedure used was described in O. Lohse, P. Thevenin,
E. Waldvogel Synlett, 1999, 45-48. In a typical experiment, a mixture of
200 mL of degassed water, 20 g of potassium carbonate, 150 mL of
1,2-dimethoxyethane, 0.5 g of Pd(PPh3)4, 0.05 mol of a
substituted 2-chloropyridine (quinoline or pyrimidine) and 0.05 mol of a
substituted phenylboronic acid was refluxed (80-90° C.) for 16 to
30 h. The resulting reaction mixture was diluted with 300 mL of water and
extracted with CH2Cl2 (2×100 mL). The combined organic
layers were dried over MgSO4, and the solvent removed by vacuum. The
liquid products were purified by fractional vacuum distillation. The
solid materials were recrystallized from hexane. The typical purity of
isolated materials was >98%. The starting materials, yields, melting
and boiling points of the new materials are given in Table 3. NMR data
and analytical data are given in Table 4.

[0107]In a typical experiment, a mixture of IrCl3.nH2O (53-55%
Ir), AgOCOCF3 (3.1 equivalents per Ir), 2-arylpyridine (excess), and
(optionally) a small amount of water was vigorously stirred under N2
at 180-195° C. (oil bath) for 2 to 8 hours. The resulting mixture
was thoroughly extracted with CH2Cl2 until the extracts were
colorless. The extracts were filtered through a silica column to produce
a clear yellow solution. Evaporation of this solution gave a residue
which was treated with methanol to produce colored crystalline
tris-cyclometalated Ir complexes. The complexes were separated by
filtration, washed with methanol, dried under vacuum, and (optionally)
purified by crystallization, vacuum sublimation, or Soxhlet extraction.
Yields: 10-82%. All materials were characterized by NMR spectroscopic
data and elemental analysis, and the results are given in Table 5 below.
Single-crystal X-ray structures were obtained for three complexes of the
series.

Compound 1-b

[0108]A mixture of IrCl3.nH2O (54% Ir; 508 mg),
2-(4-fluorophenyl)-5-trifluoromethylpyridine, compound kk (2.20 g),
AgOCOCF3 (1.01 g), and water (1 mL) was vigorously stirred under a
flow of N2 as the temperature was slowly (30 min) brought up to
185° C. (oil bath). After 2 hours at 185-190° C. the
mixture solidified. The mixture was cooled down to room temperature. The
solids were extracted with dichloromethane until the extracts
decolorized. The combined dichloromethane solutions were filtered through
a short silica column and evaporated. After methanol (50 mL) was added to
the residue the flask was kept at -10° C. overnight. The yellow
precipitate of the tris-cyclometalated complex, compound b, was
separated, washed with methanol, and dried under vacuum. Yield: 1.07 g
(82%). X-Ray quality crystals of the complex were obtained by slowly
cooling its warm solution in 1,2-dichloroethane.

Compound 1-e

[0109]A mixture of IrCl3.nH2O (54% Ir; 504 mg),
2-(3-trifluoromethylphenyl)-5-trifluoromethylpyridine, compound bb (1.60
g), and AgOCOCF3 (1.01 g) was vigorously stirred under a flow of
N2 as the temperature was slowly (15 min) brought up to 192°
C. (oil bath). After 6 hours at 190-195° C. the mixture
solidified. The mixture was cooled down to room temperature. The solids
were placed on a silica column which was then washed with a large
quantity of dichloromethane. The residue after evaporation of the
filtrate was treated with methanol to produce yellow solid. The solid was
collected and purified by extraction with dichloromethane in a 25-mL
micro-Soxhlet extractor. The yellow precipitate of the
tris-cyclometalated complex, compound e, was separated, washed with
methanol, and dried under vacuum. Yield: 0.59 g (39%). X-Ray quality
crystals of the complex were obtained from hot 1,2-dichloroethane.

Compound 1-d

[0110]A mixture of IrCl3.nH2O (54% Ir; 508 mg),
2-(2-fluorophenyl)-5-trifluoromethylpyridine, compound aa (1.53 g), and
AgOCOCF3 (1.01 g) was vigorously stirred under a flow of N2 at
190-195° C. (oil bath) for 6 h 15 min. The mixture was cooled down
to room temperature and then extracted with hot 1,2-dichloroethane. The
extracts were filtered through a short silica column and evaporated.
Treatment of the residue with methanol (20 mL) resulted in precipitation
of the desired product, compound d, which was separated by filtration,
washed with methanol, and dried under vacuum. Yield: 0.63 g (49%). X-Ray
quality crystals of the complex were obtained from
dichloromethane/methanol.

Compound 1-i

[0111]A mixture of IrCl3.nH2O (54% Ir; 503 mg),
2-(4-trifluoromethoxyphenyl)-5-trifluoromethylpyridine, compound ee (2.00
g), and AgOCOCF3 (1.10 g) was vigorously stirred under a flow of
N2 at 190-195° C. (oil bath) for 2 h 45 min. The mixture was
cooled down to room temperature and then extracted with dichloromethane.
The extracts were filtered through a short silica column and evaporated.
Treatment of the residue with methanol (20 mL) resulted in precipitation
of the desired product, compound i, which was separated by filtration,
washed with methanol, and dried under vacuum. The yield was 0.86 g.
Additionally, 0.27 g of the complex was obtained by evaporating the
mother liquor and adding petroleum ether to the residue. Overall yield:
1.13 g (72%).

Compound 1-q

[0112]A mixture of IrCl3.nH2O (54% Ir; 530 mg),
2-(3-methoxyphenyl)-5-trifluoromethylpyridine (2.50 g), AgOCOCF3
(1.12 g), and water (1 mL) was vigorously stirred under a flow of N2
as the temperature was slowly (30 min) brought up to 185° C. (oil
bath). After 1 hour at 185° C. the mixture solidified. The mixture
was cooled down to room temperature. The solids were extracted with
dichloromethane until the extracts decolorized. The combined
dichloromethane solutions were filtered through a short silica column and
evaporated. The residue was washed with hexanes and then recrystallized
from 1,2-dichloroethane-hexanes (twice). Yield: 0.30 g. 19F NMR
(CD2Cl2, 20° C.), δ: -63(s). 1H NMR
(CD2Cl2, 20° C.), δ: 8.1 (1H), 7.9 (1H), 7.8 (1H),
7.4 (1H), 6.6 (2H), 4.8 (3H). X-Ray quality crystals of the complex
(1,2-dichloroethane, hexane solvate) were obtained from
1,2-dichloroethane-hexanes. This facial complex was
orange-photoluminescent.

[0113]Compounds 1-a, 1-c, 1-f through 1-h, 1-j through 1-m, and 1-r were
similarly prepared. In the preparation of compound 1-j, a mixture of
isomers was obtained with the fluorine in either the R6 or R8
position.

[0114]This example illustrates the preparation of iridium complexes of the
Second Formula IrLaLbLcxL'yL''z above,

Compound 1-n

[0115]A mixture of IrCl3.nH2O (54% Ir; 510 mg),
2-(3-trifluoromethylphenyl)quinoline (1.80 g), and silver
trifluoroacetate (1.10 g) was vigorously stirred at 190-195° C.
for 4 hours. The resulting solid was chromatographed on silica with
dichloromethane to produce a mixture of the dicyclometalated complex and
the unreacted ligand. The latter was removed from the mixture by
extraction with warm hexanes. After the extracts became colorless the
hexane-insoluble solid was collected and dried under vacuum. The yield
was 0.29 g. 19F NMR: -63.5 (s, 6F), -76.5 (s, 3F). The structure of
this complex was established by a single crystal X ray diffraction study.

Compound 1-o

[0116]A mixture of IrCl3.nH2O (54% Ir; 500 mg),
2-(2-fluorophenyl)-3-chloro-5-trifluoromethylpyridine (2.22 g), water
(0.3 mL), and silver trifluoroacetate (1.00 g) was stirred at 190°
C. for 1.5 hours. The solid product was chromatographed on silica with
dichloromethane to produce 0.33 g of a 2:1 co-crystallized adduct of the
dicyclometalated aqua trifluoroacetato complex, compound 1-p, and the
unreacted ligand. 19F NMR: -63.0 (9F), -76.5 (3F), -87.7 (2F),
-114.4 (1 F). The co-crystallized phenylpyridine ligand was removed by
recrystallization from dichloromethane-hexanes. The structures of both
the adduct and the complex were established by a single crystal X-ray
diffraction study.

[0128]This example illustrates the formation of OLEDs using the iridium
complexes of the invention.

[0129]Thin film OLED devices including a hole transport layer (HT layer),
electroluminescent layer (EL layer) and at least one electron transport
layer (ET layer) were fabricated by the thermal evaporation technique. An
Edward Auto 306 evaporator with oil diffusion pump was used. The base
vacuum for all of the thin film deposition was in the range of 10-6
torr. The deposition chamber was capable of depositing five different
films without the need to break up the vacuum.

[0130]An indium tin oxide (ITO) coated glass substrate was used, having an
ITO layer of about 1000-2000 Å. The substrate was first patterned by
etching away the unwanted ITO area with 1N HCl solution, to form a first
electrode pattern. Polyimide tape was used as the mask. The patterned ITO
substrates were then cleaned ultrasonically in aqueous detergent
solution. The substrates were then rinsed with distilled water, followed
by isopropanol, and then degreased in toluene vapor for ˜3 hours.

[0131]The cleaned, patterned ITO substrate was then loaded into the vacuum
chamber and the chamber was pumped down to 10-6 torr. The substrate
was then further cleaned using an oxygen plasma for about 5-10 minutes.
After cleaning, multiple layers of thin films were then deposited
sequentially onto the substrate by thermal evaporation. Finally,
patterned metal electrodes of Al were deposited through a mask. The
thickness of the film was measured during deposition using a quartz
crystal monitor (Sycon STC-200). All film thickness reported in the
Examples are nominal, calculated assuming the density of the material
deposited to be one. The completed OLED device was then taken out of the
vacuum chamber and characterized immediately without encapsulation.

[0132]A summary of the device layers and thicknesses is given in Table 6.
In all cases the anode was ITO as discussed above, and the cathode was Al
having a thickness in the range of 700-760 Å. In some of the samples,
a two-layer electron transport layer was used. The layer indicated first
was applied adjacent to the EL layer.

[0133]The OLED samples were characterized by measuring their (1)
current-voltage (I-V) curves, (2) electroluminescence radiance versus
voltage, and (3) electroluminescence spectra versus voltage. The
apparatus used, 200, is shown in FIG. 2. The I-V curves of an OLED
sample, 220, were measured with a Keithley Source-Measurement Unit Model
237, 280. The electroluminescence radiance (in the unit of Cd/m2)
vs. voltage was measured with a Minolta LS-110 luminescence meter, 210,
while the voltage was scanned using the Keithley SMU. The
electroluminescence spectrum was obtained by collecting light using a
pair of lenses, 230, through an electronic shutter, 240, dispersed
through a spectrograph, 250, and then measured with a diode array
detector, 260. All three measurements were performed at the same time and
controlled by a computer, 270. The efficiency of the device at certain
voltage is determined by dividing the electroluminescence radiance of the
LED by the current density needed to run the device. The unit is in Cd/A.

[0135]The peak efficiency is the best indication of the value of the
electroluminescent compound in a device. It gives a measure of how many
electrons have to be input into a device in order to get a certain number
of photons out (radiance). It is a fundamentally important number, which
reflects the intrinsic efficiency of the light-emitting material. It is
also important for practical applications, since higher efficiency means
that fewer electrons are needed in order to achieve the same radiance,
which in turn means lower power consumption. Higher efficiency devices
also tend to have longer lifetimes, since a higher proportion of injected
electrons are converted to photons, instead of generating heat or causing
an undesirable chemical side reactions. Most of the iridium complexes of
the invention have much higher peak efficiencies than the parent
fac-tris(2-phenylpyridine) iridium complex. Those complexes with lower
efficiencies may also find utility as phosphorescent or photoluminescent
materials, or as catalysts, as discussed above.

[0142]Compounds 8-a through 8-k, and compound 8-s in Table 8 were prepared
using a similar procedure.

[0143]Compounds 8-l through 8-q in Table 8 were prepared using the
procedure of Example 2.

Example 11

[0144]Thin film OLED devices were fabricated using the procedure according
to Example 7. A summary of the device layers and thicknesses is given in
Table 10. In all cases the anode was ITO as discussed above, and the
cathode was Al having a thickness in the range of 700-760 Å.

[0149]2-(2',4'-dimethoxyphenyl)-5-trifluoromethylpyridine was prepared via
Kumada coupling of 2-chloro-5-trifluoromethylpyridine with
2,4-dimethoxyphenylmagnesium bromide in the presence of
[(dppb)PdCl2] catalyst (dppb=1,4-bis(diphenylphosphino)butane).

[0153]A mixture of a the dichloro-bridged dinuclear bis-cyclometallated Ir
complex made as in Example 13, a monodentate ligand L', and
1,2-dichloroethane (DCE) or toluene was stirred under reflux (N2 or
CO when L' is CO) until all solids dissolved and then for additional 3
min -1 h. The products were isolated and purified by evaporation and
crystallization in air. Detailed procedures for selected complexes are
given below. All complexes were characterized by NMR spectroscopic data
(31P NMR=31P-{1H} NMR). Satisfactory combustion analyses
were not obtained due to insufficient thermal stability of the complexes.
Both isomers of compound 9-k, the major isomer with the nitrogens trans
and the minor isomer with the nitrogens cis, were characterized by
single-crystal X-ray diffraction.

[0159]Complexes 9-a, 9-b, 9-c, 9-e, 9-f, 9-h, and 9-i, were made using the
same procedure as for complex 9-d, using phenylpyridine compounds 12-a,
12-c, 12-g, 12-d, 2-k, 12-f, and 2-k, respectively.

Example 15

[0160]Thin film OLED devices were fabricated using the procedure according
to Example 7. A summary of the device layers and thicknesses is given in
Table 14. In all cases the anode was ITO as discussed above, and the
cathode was Al having a thickness in the range of 700-760 Å.